Hier-Majumder S., and Revenaugh, J. (2010) The relationship between the viscosity and topography of the Ultra Low Velocity Zone near the core-mantle boundary, Earth and Planetary Science Letters, 299, 382-386
(link)

2007

Papers:

Cammarano, F. and Romanowicz, B. (2007) Insights into the nature of the transition zone from physically constrained inversion of long period seismic data, Proceedings of the National Academy of Sciences, 104, 9139-9144
(link)